Soil
Soil contains small particles of decomposed rocks and minerals in the form of sand, silt, and clay. Soil consists of many layers called horizons. The top horizon is generally called top soil. Top soil is a mixture of mineral matter, decayed plant and animal organic matter, and micro and macroorganisms, such as bacteria, fungi, nematodes and worms. The literature estimates that it takes between 500 and 1000 years for nature to make one inch of topsoil. On the other side, through agricultural, mining and deforestation practices topsoil is being lost and degraded rapidly around the world. The U.S. Department of Agriculture (USDA) estimates that the United States alone loses almost three tons of topsoil per acre per year (“Summary Report, 2007 Natural Resources Inventory”, Natural Resources Conservation Services, U.S. Department of Agriculture. December 2009. p. 97). Small particles are more easily lost to erosion than larger particles.
Soil Texture
Particle size is classified by the USDA into three main groupings: sand, silt and clay (other countries have other systems, though they are comparable). Clay particle sizes are defined as less than 2 μm. Particles between 2 μm and 50 μm are classified as silt. Particles from 50 μm to 2 mm are considered sand. Note that the clay, silt, and sand size classifications do not denote the chemical nature of the particle, just the size classification. Ideal particle balanced soil texture is classified as loam. Loam consists generally of about 40% sand, 40% silt, and 20% clay particles. Very few agricultural fields have the ideal soil texture of loam. In many cases silt and clay have been lost due to erosion. There is a need in the art to provide a method for improving soil texture or the balance of sand, silt and clay.
Mineral and Nutrient Content
Nutrients are essential for healthy plant growth. Most plant nutrients originate from fine silt and clay soil particles. Yet many soils have lost the fine-sized silt and clay and their associated nutrients. There is a need in the art to provide a method for improving agricultural soil nutrient characteristics to promote healthy plant growth and ultimately good human nutrition.